Hi,
I was on OPT from January through July 2006, I did not work August and September and resumed working in H1B status in October. Even while on OPT taxes were withheld for social security and medicare. Should I file taxes separately? One for while on OPT and the other for while on H1B? The company just gave one W2, so I'm not sure what to do.
I am claiming my brother as a dependent, since he is on F1 status. He has no income, we share an apartment and I pay his tuition. Any suggestions/advice/help would be greatly appreciated.
Thanks.

You first msut ask the employer to refund the improperly-withheld SS and Medicae taxes. If refused, get the refusal in writing, preferably on company letterhead. Then complete and submit Form843 along with the support documents specified on page 46 of IRS Pub 519 to request a refund of the SS and Medicare taxes.

You only file ONE federal tax return. Just combined the data from the two W-2s.

You CANNOT claim your brother as a dependent, because he is NOT a legal resident of the U.S. (his F-1 visa puts him in a non-resident alien status).